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I often camp in rainy or very humid weather, and I often have condensation forming inside my tent. What can I do to minimize this?

My tent has vents, but I’m not sure how to make the best use of them. I’m not sure if I should just leave them open all the time, or if there’s something more clever to do.

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Are you intentionally keeping the tent sealed? Condensation on the inside is either bringing a lot of damp clothing into the tent without sealing it in bags or the moisture breathed out by the inhabitants? You might control the first but a tent with more ventilation is the only countermeasure for the second. –  bmike Feb 7 '12 at 15:36
    
I don’t try to keep the tent sealed... I usually just leave the vents open and hope for the best. Like I said, I'm often in very humid weather, something like 25ºC with over 90% relative humidity, so I think a lot of the humidity is just from the air (other than, as you mentioned moisture, what’s produced by the inhabitants). –  Big General Feb 7 '12 at 16:04
    
Wow - odd conditions (for where I camp). I'm more used to weather conditions making condensation on top and outer surfaces of the tent and rain fly, with inhabitants making the condensation on the inside of the tent. I hope someone has a good answer - I'm intrigued. –  bmike Feb 7 '12 at 16:08
    
I'd like to know, too. We have horrendous issues with condensation on the inside of the tent during the winter-- and that's definitely produced by the inhabitants. –  Clare Steen Feb 7 '12 at 16:45
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Please specify more about your tent: single wall? interior breathable walls plus waterproof fly? interior mesh plus waterproof fly? –  Bryce Feb 8 '12 at 4:36

7 Answers 7

up vote 16 down vote accepted

If it's raining or very humid you are probably going to have to put up with some condensation, but to try and reduce it, look for ways to minimise water vapour and increase ventilation. The following may help, but obviously not all will be appropriate for the conditions you are camping in.

Sources of water vapour:

  • Combustion of fuel in a stove and steam from cooking - avoid cooking in the vestibule of your tent (I'm assuming you wouldn't be cooking fully in your tent).
  • Steam from food - avoid eating hot food in your tent.
  • Respiration/perspiration - is the tent overcrowded?
  • Wet gear - avoid bringing wet gear into the tent unless you are trying to dry it. Pack wet gear in a survival bag and leave it outside the tent.
  • Location - avoid camping close to marsh or other bodies of water (obviously this needs to be balanced with proximity to a source of water for cooking/cleaning).
  • Under-tent conditions - look for dry ground to camp on, avoid thick vegetation that may be a source of water vapour.

Other tips:

  • Consider an elevated camp position, the bottom of a valley may become colder at night increasing condensation. There may also be more of a breeze to help ventilate your tent.
  • Pitch your tent such that the vents are aligned with the prevalent wind to maximise air flow through your tent. Obviously in high winds you should still pitch you tent to minimise the chance of it being damaged or blowing away.
  • If weather and biting insects allow, keep the tent door open to maximise ventilation.
  • Single walled tents, while small and light, are less effective in humid conditions. If you are using such a tent, make sure it is designed to be easily ventilated.
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Everything here is great. A tarp or footprint underneath the tent can greatly reduce exposure to ground moisture. –  Ryan Nov 27 '12 at 22:12

A tent shell causes a convection effect - warmer air rises from you (especially from respiration) and cools when it contacts the tent interior, which is cooled by the outside air. Some of the cooler air passes outside, but some of it settles back down on you and the process repeats.

You can reduce this process in ways explained above: notably, opening the tent as wide as possible to air currents. Opening ventilation windows will break up the convection effect and deprive the warmer, rising air of a surface to dump its moisture on. Because the tent doesn't provide much insulation, you really won't lose much by doing so. Your sleeping bag is responsible for keeping you warm and cozy on such nights. It goes without saying, incidentally, that in humid conditions like that (or where I live, on the East Coast of the USA), you should be using synthetic sleeping bags and clothing as much as possible.

Another thing to do is to experiment with your use of the rain fly. At points where the rain fly touches the tent, condensation tends to occur more because less moisture-laden air escapes through the waterproof fly. At places where the fly does not make contact with the tent, but sits a few inches above it, moisture condensing on it tends to follow the contours of the fly off the top of the tent and then down onto the sides. This speaks to two things to look for in a rain fly and tent construction when making your next purchase: (1) the fly ought to be long and broad, not one of those dinky little beanie-type things; (2) it the fly ought not rest on the body of the tent, but on the poles, held away from the tent.

If your rain fly fails in these regards, rather than rush off and buy a new tent, try getting a tarp and hanging it over the tent across a line and anchoring it on the corners, like a big A-tent close over your tent. Then keep your tent as open as possible to ventilate it without letting in rain or uncomfortable amounts of wind. I've never tried this idea because my Sierra Designs Omega is awesome, but I'd like to know whether it helps. I'm convinced the theory is sound.

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I would say experiment with news paper or roll paper, because it will absorb vapor while staying mostly dry, it does not weigh much, and news paper or paper from wide rolls are great insulation, and breathable.

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How would this work? Sure paper is insulation but... are you proposing I stick it to my tent walls before going to sleep? –  Russell Steen Nov 26 '12 at 14:47

If the rain stops you can pull your sleeping bag out and turn it inside out to air out on a line or branch. If you can't get out of the rain use your stove to heat up a few large rocks in a pot or pan. Use smooth river rocks as poorious rocks my burst under steam pressure, if your not sure just put a lid on. When rocks are hot carefully place pot in tent with something under the pot ( like a second pot or pan turned upside down). Enjoy.

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Build the tent under the tree to reduce morning dew, and so that it is not shaded from the morning sun. And possibly try to avoid building it on a wet surface. Open the ventilation holes placed at the very top of the tent. If you have a wet towel or other very wet clothes, place it outside of the tent (not in the vestibule of the tent, as advised in another answer).

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Out of curiosity, why not use the vestibule ? –  Amine Aug 30 '12 at 14:41
    
@Amine if you leave a wet towel in the vestibule, the tent will be wet of the condensated water in the vestibule. –  Tomas Sep 29 '12 at 22:59

Unfortunately, if you're in really humid territory then it's inevitable that some condensation will form, though there are steps you can take to reduce it:

  • Leave all the vents you can open - there's not really anything "cleverer" to do with them, it's just a case of them letting the moist air out.

  • If conditions (and safety) allows, consider leaving the door open - it'll essentially act as a massive vent and should help things.

  • Minimize the amount of wet material you bring into the tent, preferably don't bring any in unless you have no other option. The moisture will evaporate and increase the humidity further, only exaggerating the problem.

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  • If it's not actually raining, leave as many vestibule doors/tent doors as possible completely open.
  • Within reason, setup somewhere that will have breezes but hopefully not so exposed that a big wind will steal your tent :)
  • Consider using a less-confining tent for those conditions. i.e. a tarp
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I ALWAYS leave the top vent open (I have a rain-fly that completely covers it. and this is one of the best way to reduce condensation –  mjrider Feb 8 '12 at 16:43

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